We have been developing computer-assisted interactive techniques using microdensitometry and surface display facilities to perform micromorphometric analyses of hypertrophied myocardium from humans and from experimental animal preparations. Our techniques have the ability to analyze approximately 202,500 samples (pixels) from a photomicrograph of a tissue specimen. The size of the sample is determined by the magnification of the photomicrograph. Depending upon the information required, magnifications vary from 10 to 860 x, so that resolutions may be varied from 5 to 0.5 millimicrons. Techniques developed thus far allow the ability to determine percent fibrosis, percent interstitium, cardiac muscle cells diameter and shape, uniformity of cell shape and size, and ratios of cardiac muscle area to numbers of nuclei and to numbers of capillaries.